Estrogen receptors in the mouse are not relegated to reproductive tissues alone but are also present in nonreproductive tissues. Purification of receptors from mouse uterus and kidney will be undertaken in order to compare their chemical differences and similarities as well as their interaction with homologous DNA and chromatin. Specific and nonspecific receptor binding to DNA will be analyzed using purified fractions of mouse DNA obtained by hydrolysis with bacterial restriction endonucleases.